The present invention relates to the measurement of indoor atmospheric corrosivity particularly with respect to its harmful characteristics on electronic equipment. Pulp Mills, Oil Refineries and other related industries generate corrosive gases which are harmful to the circuitry in electronic equipment. Such gases include sulfur dioxide, hydrogen sulfide, hydrogen chloride and chlorine dioxide for example. These gases even at parts-per-billion concentrations, which are far below what is permissible for humans, can lead to the failure of computer control equipment due to corrosion of circuitry in as little time as several months, depending upon the corrosive gas concentration, temperature and humidity. Because of the potential of costly down time from such failures, and safety concerns, industries are spending millions of dollars each year purifying computer control room atmospheres and measuring the corrosivity of such atmospheres.
At the present time, the standard industry method for measuring the corrosivity of the atmosphere in a computer control room is to expose a clean copper strip to the atmosphere for 1-3 months, and subsequently determine the amount of corrosion product developed by electrochemically converting the oxidized copper back to metallic copper. By measuring the amount of electrical charge needed for the above conversion, the amount of copper that corroded in the time period of exposure can be calculated. The disadvantage of this method is that it is labor intensive and requires costly analysis and measurement of the corrosion products after the exposure period. Obviously it would be far preferable to have available a monitoring device which would enable one to measure and record the corrosivity of the atmosphere continuously and to relate the corrosivity to as many variables as possible.
In the present invention, the atmospheric monitoring device is self contained and powered. The device includes sensors for temperature, relative humidity, pressure and corrosion indicators. These sensors sense atmospheric conditions and generate inputs to a microprocessor. The microprocessor scans the signals generated and records in a memory module excursions from set conditions which last for more than a designated time period. The result is an integrated record of the atmospheric conditions monitored on a time zero scale. Spurious momentary changes in conditions are ignored, but a full history of both regular and irregular excursions from a set of specified conditions is recorded.
Related prior art in the general area of the present invention includes U.S. Pat. Nos. 4,114,450 and 4,503,707. In the first patent, a self contained and internally powered shock, temperature and relative humidity acquisition and recording device is disclosed. In the latter patent, a hygrometry probe is disclosed for sensing moisture, temperature and pressure, linearizing the moisture measurement, and providing a digital output indicative of the linearized moisture, temperature and pressure.